Method for producing a sensor

ABSTRACT

A method for producing a sensor which is equipped to detect a physical field as a function of a dimension to be measured using a measuring sensor and to emit an electrical output signal based on the detected physical field via a data cable, including:—placing the measuring sensor and the data cable on a mould defining the position of the measuring sensor and the data cable,—Coating the measuring sensor and the data cable positioned in the mould with a first material,—Removing the measuring sensor and data cable coated with the first material from the mould, and—Coating the measuring sensor and data cable removed from the mould and coated with the first material with a second material.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase Application of PCT International Application No. PCT/EP2014/071588, filed Oct. 8, 2014, which claims priority to German Patent Application No. 10 2013 224 464.9, filed Nov. 28, 2013 and German Patent Application No. 10 2014 208 425.3, filed May 6, 2014, the contents of such applications being incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to a method for producing a sensor and to the sensor produced by the method.

BACKGROUND OF THE INVENTION

WO 2010/037 810 A1, which is incorporated by reference discloses a sensor for outputting an electrical signal which is dependent on a physical variable which is detected by means of a physical field on the basis of a measuring sensor.

SUMMARY OF THE INVENTION

An aspect of the invention aims to improve the known sensor.

According to one aspect of the invention, a method for producing a sensor which is configured to detect a physical field, dependent on a variable to be measured, by means of a measuring sensor, and to output an electrical output signal on the basis of the detected physical field via a data cable, comprises the steps:

-   -   placing the measuring sensor and the data cable in a mold which         defines the position of the measuring sensor and of the data         cable,     -   encapsulating the measuring sensor and data cable positioned in         the mold with a first material,     -   removing the measuring sensor and data cable encapsulated with         the first material from the mold, and     -   encapsulating the measuring sensor and data cable encapsulated         with the first material and removed from the mold with a second         material.

The specified method is based on the idea that the measuring sensor and the data cable have to be enclosed completely by at least one of the two materials for both elements to be protected from moisture and other influences which bring about weathering. In order to enclose the two elements, they can be placed in a mold, which is then, for example, filled with the first material by injection molding. However, the problem basically arises here that part of the elements always rest on the edge of the mold, and therefore no complete seal is possible with the material at these locations because the elements cannot be encapsulated with the material at these locations.

Although, for example, by using a securing mechanism the measuring sensor can be secured in such a way that all the elements can be encapsulated completely with the material, the measuring sensor must be positioned in this securing mechanism, which, in particular owing to the rigidity of the cable, is only possible to a limited degree within sufficient tolerances. In addition, the use of the measuring sensor in the securing mechanism requires additional fabrication steps, and also the securing mechanism cannot be completely encapsulated, as a result of which gaps remain through which the abovementioned moisture can penetrate and reach the measuring sensor and/or the data cable.

Within the scope of the specified method, a different approach is therefore adopted. Here, the measuring sensor with the data cable is encapsulated with the first material in a first step. In the process, no consideration is given to whether the measuring sensor and/or the data cable are partially exposed and have locations which are not encapsulated by the first material. Instead, the measuring sensor and the data cable can be positioned highly precisely when they are encapsulated with the first material by injection molding. Only subsequently, during the encapsulation with the second material by injection molding, are the measuring sensor and the data cable encapsulated in such a way that no exposed locations which are subjected to moisture or other influences which produce weathering remain on these elements. In this way, a sensor can be produced with a highly precisely positioned measuring sensor which is resistant to the influences of the weather such as moisture.

In one development of the specified method, the mold comprises a positioning element in which the measuring sensor is positioned. This positioning element can be made available in any desired way like, for example, the abovementioned securing mechanism. The highly precise position of the measuring sensor can be implemented with a simple means by virtue of the positioning element.

In an additional development of the specified method, the mold comprises a shaping element on which the measuring sensor is shaped before or during the encapsulation with the first material. With the shaping element, the data cable and the measuring sensor can be placed in the mold which they require for the final application, during the encapsulation of the first material. In this way, the clocking times while the specified method is carried out can be reduced.

In a particular development of the specified method, the shaping element is a bending element. With such a bending element, the measuring sensor can be bent into a position in which it can detect the abovementioned physical field particularly favorably.

In another development, the specified method comprises the step of molding a positively locking element in the first material during the encapsulation of the measuring sensor and data cable, positioned in the mold, with a first material. This positively locking element can be used to connect the measuring sensor and the data cable, which are surrounded by the first material, to further elements.

In one preferred development, the specified method comprises the step of molding a sealing contour around the positively locking element during the encapsulation of the measuring sensor and data cable, positioned in the mold, with a first material. The previously mentioned further element could form, after the encapsulation with the second material, a gap between the further element and the second material. In this context, there is basically the risk of the abovementioned moisture being able to penetrate via this gap. As a result of the sealing element, this risk of penetration can be reduced, if not entirely avoided.

In one particularly preferred development, the specified method comprises the step of inserting a securing element into the positively locking element, to which securing element the measuring sensor, encapsulated with the first material, and the data cable can be secured after the encapsulation with the first material. In this way, the first material can be completely surrounded by the second material without exposed locations remaining on the first material, with the result that a high degree of leakproofness can be achieved with the second material.

In a further development of the specified method, the measuring sensor, encapsulated with the first material and removed from the mold, and the data cable are encapsulated with a second material in a non-cured state of the first material. In this way, the first material and the second material can be connected to one another during the encapsulation with the second material, with the result that gaps between the first material and the second material are closed.

In yet another development, the specified method comprises the step of forming a sealing contour which, when viewed in the direction of the data cable, runs around the first material and is arranged on the first material on a side of the data cable lying opposite the measuring sensor. This sealing element makes it possible to avoid a situation in which moisture penetrates the produced sensor at a connection point for the data cable.

According to a further aspect of the invention, a sensor for detecting a physical field, dependent on a variable to be measured, by means of a measuring sensor and for outputting an electrical output signal on the basis of the detected physical field by means of a data cable is produced by means of a specified method.

According to a further aspect of the invention, a mold for use in one of the specified methods comprises a first mold part, and a second mold part which can be placed on the first mold part, wherein the two mold parts form, in the state in which they are placed one on the other, a casting cavity in which the data cable, the measuring sensor and the first material can be at least partially accommodated, and wherein a bending die is formed on the first mold part, and a recess is formed on the second mold part, for accommodating the bending die, by means of which bending die and recess the measuring sensor can be shaped when the second mold part is placed on the first mold part.

The specified mold can be extended with the positioning aid specified above as well as the abovementioned sealing mold regions.

BRIEF DESCRIPTION OF THE DRAWINGS

The properties, features and advantages of this invention which are described above and the way in which they are achieved become clearer and more easily understandable in conjunction with the following description of the exemplary embodiments which are explained in more detail in conjunction with the drawings, wherein:

FIG. 1 shows a schematic view of a vehicle with a vehicle dynamics control system,

FIG. 2 shows a schematic view of a rotation speed sensor in the vehicle in FIG. 1,

FIG. 3 shows a schematic view of a method sequence for producing a part of the rotational speed sensor in FIG. 2,

FIG. 4 shows an illustration of a detail of the schematic view in FIG. 3,

FIG. 5 shows an illustration of a detail of the schematic view in FIG. 4, and

FIG. 6 shows a schematic view of an alternative method sequence for producing a part of the rotational speed sensor in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the figures, identical technical elements are provided with identical reference symbols and are described only once.

Reference is made to FIG. 1 which shows a schematic view of a vehicle 2 with a vehicle dynamics control system which is known per se. Details on this vehicle dynamics control system can be found, for example, in DE 10 2011 080 789 Al, which is incorporated by reference.

The vehicle 2 comprises a chassis 4 and four wheels 6. Each wheel 6 can be slowed down with respect to the chassis 4 by means of a brake 8 which is attached in a positionally fixed fashion to the chassis 4, in order to slow down the movement of the vehicle 2 on a road (not illustrated further).

In this context, it is possible that, in a manner known to a person skilled in the art, the wheels 6 of the vehicle 2 lose their grip and the vehicle 2 is moved away even from a trajectory which is predefined, for example, by means of a steering wheel (not shown further), as a result of understeering or oversteering. This is avoided by closed-loop control circuits which are known per se such as ABS (anti-lock brake system) and ESP (electronic stability program).

In the present embodiment, the vehicle 2 has for this purpose rotational speed sensors 10 on the wheels 6 which detect the rotational speed 12 of the wheels 6. In addition, the vehicle 2 has an inertial sensor 14 which detects movement dynamics data 16 of the vehicle 2 from which, for example, a pitch rate, a rolling rate, a yaw rate, a lateral acceleration, a longitudinal acceleration and/or a vertical acceleration can be output in a manner known per se to a person skilled in the art.

On the basis of the detected rotational speeds 12 and movement dynamics data 16, a controller 18 can determine, in a manner known to a person skilled in the art, whether the vehicle 2 is slipping on the underlying surface or even deviating from the abovementioned, predefined trajectory, and said controller 18 can correspondingly react thereto with a controller output signal 20 which is known per se. The controller output signal 20 can then be used by an actuating device 22 in order to drive, by means of actuation signals 24, actuating elements such as the brakes 8 which react to the slipping and the deviation from the predefined trajectory in a manner known per se.

The present invention will now be explained in more detail on the basis of the rotational speed sensor 10 shown in FIG. 1, even if the present invention can be implemented in any desired electronic devices and, in particular, in any desired sensors such as magnetic field sensors, acceleration sensors, rotational speed sensors, solid-borne sound sensors or temperature sensors.

Reference is made to FIG. 2 which shows a schematic view of the rotational speed sensor 10 in the vehicle 2 in FIG. 1.

The rotational speed sensor 10 is embodied in the present embodiment as an active rotational speed sensor 10, within the scope of which an encoder disk 26, which is connected in a rotationally fixed fashion to one of the wheels 6 and is composed of a multiplicity of magnetic poles 28 outputs a magnetic field 30. The magnetic field 30 penetrates a measuring sensor 34 which is housed in a housing 32 and is connected via a signal-conditioning circuit 36 to a data cable 38 via which the rotational speed 12 can be transmitted to the controller 18. In this context, the measuring sensor 34, the signal-conditioning circuit 36 and the data cable 38 can be connected to one another by means of wiring connections 40, for example in the form of a leadframe.

Further background information on active rotational speed sensors can be found, for example, in DE 101 46 949 A1, which is incorporated by reference.

Reference is made to FIGS. 3 to 5 which show a schematic view of a method sequence for the production of a part 42 of the rotational speed sensor 10 in FIG. 2.

In this context, the part 42 of the rotational speed sensor 10 is illustrated in various fabrication stages 43 to 48, which are not illustrated in a progressive sequence in terms of the execution of the production method in FIGS. 3 to 5. For the sake of clarity, identical elements within the individual fabrication stages are provided with a reference symbol only once in FIGS. 3 to 5.

The method starts in the first fabrication stage 43 with the measuring sensor 34, the signal-conditioning circuit 36 and the data cable 38 being connected to one another via the wiring connections 40. In this context, the wiring connections 40 have positioning openings 49 between the signal-conditioning circuit 36 and the data cable 38.

Within the scope of the second fabrication stage 44, the circuit composed of the measuring sensor 34 connected in this way, the signal-conditioning circuit 36 and the data cable 38 are accommodated in a lower mold part 50 of a first molding. Details on how this circuit is inserted into the lower mold part and how the lower mold part 50 is constructed will be explained below with reference to the exploded illustration within the scope of the third fabrication stage 45.

The lower mold part 50 comprises two receptacle openings 51 in which positioning elements in the form of positioning pins 52 can be inserted. The abovementioned positioning openings 49 are fitted onto these positioning pins 52, as can be seen in the second fabrication stage 44.

In addition, the lower mold part 50 comprises a bending die 53, on which the wiring connection 40 between the measuring sensor 34 and the evaluation circuit 36 is placed. The measuring sensor 34 is bent with respect to the evaluation circuit 36 by means of the bending die 53 within the scope of the production method, as will be explained in more detail later, with the result that the measuring sensor 34 can be bent parallel to the encoder disk 26 for optimum detection of the magnetic field 30. This bent state is already illustrated within the scope of the second fabrication stage 44. However, in the unbent state of the measuring sensor 34, the circuit is inserted into the lower mold part 50.

The lower mold part 50 also has a holding mold region 54, via which a holding mold 55, to be described later below, can be formed on an intermediate housing 56 which is to be molded with the first mold. More details on this are given at a later location. A sealing mold region 57, with which a sealing mold 58 can be formed around the holding mold 55, on the intermediate housing, is formed around this holding mold region 54. A similar further sealing mold region 57 can be formed on the cable-side end of the lower mold part 50.

In the next, third fabrication step 44, an upper mold part 59, which is associated with the first mold, is arranged above the lower mold part 50, said mold part 59 being illustrated in a cut-away form in FIGS. 3 to 5. The upper mold part 59 has in a similar way to the lower mold part 50, a holding mold region 54 and two sealing mold regions 57, which are, however, not provided with a reference symbol in FIGS. 3 to 5 for the sake of clarity. In addition, the upper mold part 59 has a recess 60 in which the bending die 53 can be accommodated.

This upper mold part 59 is then moved, within the scope of the fourth and fifth fabrication stages 46, 47 as shown in FIG. 3, against the lower mold part 50, with the result that the casting cavity between the two mold parts 50, 59, which casting cavity comprises, inter alia, the holding mold region 54 and the sealing mold regions 57 as well as a region which molds the intermediate housing 56 and is not provided with further references, is closed. Within the scope of this closing movement, the wiring connections 40 which are placed on the bending die 53 are bent, with the result that the measuring sensor 34 is bent into the position described above, in which it can be oriented parallel to the encoder wheel 26.

In the now closed casting cavity, a first encapsulation material, which molds the intermediate housing 56, is now input by pouring or injection molding. After initial curing of this first encapsulation material, the two mold parts 50, 59 are removed within the scope of the sixth fabrication stage 48 and inserted into one of the two holding molds 55 which are formed (above or below the intermediate housing 56), or a holding pin 61, which is embodied as a holding element, is inserted into both holding molds 55. In this context, the intermediate housing 56 can also be held in a stable way in a rear part 66 of the lower mold part 50.

As can be seen within the scope of the sixth fabrication stage 48, parts of the abovementioned circuit, such as, for example, the cable 39, are still exposed on the intermediate housing 56. In order to close these regions, a terminating housing 62 is applied by injection molding to the intermediate housing 56 which has not yet completely cured, said terminating housing 62 completely closing off these exposed regions. As a result of the fact that the terminating housing 62 is applied by injection molding to the intermediate housing 56 in a state of said intermediate housing 56 in which it is not completely cured, the terminating housing and the intermediate housing can be connected to one another better.

As a result, a rotational speed sensor 10 in which the measuring sensor 34 is enclosed in a sealed fashion and therefore protected against the ingress of moisture is provided.

Reference is made to FIG. 6 which shows a schematic view of an alternative method sequence for producing a part of the rotational speed sensor in FIG. 2.

Within the scope of this method sequence, the data cable 38 is not connected directly to the rotational speed sensor 10 but via a plug 63. In this context, the plug 63 can be cast together with the intermediate housing 56.

In this context, the measuring sensor 34 and the signal-conditioning circuit 36 are connected to a leadframe 64 by means of the wiring connection 40. The leadframe 64 can be embodied here as meterware, wherein an individual leadframe section can be cut out, for example with a punching element 65, before the molding of the intermediate housing 56. Otherwise, the production can take place in the same way as in FIGS. 3 to 5. 

1. A method for producing a sensor which is configured to detect a physical field, dependent on a variable to be measured, by a measuring sensor, and to output an electrical output signal on the basis of the detected physical field via a data cable, the method comprising: placing the measuring sensor and the data cable in a mold which defines a position of the measuring sensor and of the data cable, encapsulating the measuring sensor and data cable positioned in the mold with a first material, removing the measuring sensor and data cable encapsulated with the first material from the mold, and encapsulating the measuring sensor and data cable encapsulated with the first material and removed from the mold with a second material.
 2. The method as claimed in claim 1, wherein the mold comprises a positioning element with which the measuring sensor is positioned.
 3. The method as claimed in claim 1, wherein the mold comprises a shaping element on which the measuring sensor is shaped before or during the encapsulation with the first material.
 4. The method as claimed in claim 3, wherein the shaping element is a bending element.
 5. The method as claimed in claim 1, further comprising molding a positively locking element in the first material during the encapsulation of the measuring sensor and data cable, positioned in the mold, with the first material.
 6. The method as claimed in claim 5, further comprising molding a sealing contour around the positively locking element during the encapsulation of the measuring sensor and data cable, positioned in the mold, with a first material.
 7. The method as claimed in claim 5, further comprising inserting a securing element into the positively locking element, to which securing element the measuring sensor, encapsulated with the first material, and the data cable can be secured after the encapsulation with the first material.
 8. The method as claimed in claim 1, wherein the measuring sensor, encapsulated with the first material and removed from the mold, and the data cable are encapsulated with the second material in a non-cured state of the first material.
 9. The method as claimed in claim 1, her comprising forming a sealing contour which, when viewed in the direction of the data cable, runs around the first material, on the first material on a side of the data cable lying opposite the measuring sensor.
 10. A sensor for detecting a physical field, dependent on a variable to be measured, by a measuring sensor and for outputting an electrical output signal on the basis of the detected physical field of a data cable, which sensor is produced by a method as claimed in claim
 1. 11. A mold for use in a method as claimed in claim 1, comprising: a first mold part, and a second mold part which is configure, for placement on the first mold part, wherein the two mold parts form, when they are placed one on the other, a casting cavity in which the data cable, the measuring sensor and the first material can be at least partially accommodated, and wherein a bending die is formed on the first mold part, and a recess is formed on the second mold part, for accommodating the bending die, by which bending die and recess the measuring sensor shaped when the second mold part is placed on the first mold part.
 12. The method as claimed in claim 2, wherein the mold comprises a shaping element on which the measuring sensor is shaped before or during the encapsulation with the first material.
 13. The method as claimed in claim 6, further comprising inserting a securing element into the positively locking element, to which securing element the measuring sensor, encapsulated with the first material, and the data cable can be secured after the encapsulation with the first material. 